Abdominal pain is one of the most common reasons for children and adolescents to seek care in the emergency department (ED). Despite the high incidence, diagnosing appendicitis remains challenging. Computed tomography (CT) has been promoted as a method to improve diagnostic accuracy when evaluating patients with acute abdominal pain. In the past 20 years, CT use has increased dramatically, especially for children receiving care in general ED settings. Although in some adult cohorts, increased CT use has been associated with decreased rates of negative appendectomies, similar improvements in health outcomes among children with acute abdominal pain have not occurred. Negative consequences of CT include increased costs and substantial exposure to ionizing radiation. The proposed intervention, referred to as appy-CDS, is specifically designed for widespread use in EDs and could reduce reliance on advanced diagnostic imaging for pediatric and adolescent patients with acute abdominal pain while maintaining or improving clinical outcomes. This project builds on more than 10 years of work on derivation and validation of ED-based clinical decision rules, previous successful outpatient and emergency department clinical decision support interventions, and complex economic and statistical analyses of risk assessment and ED resource use. In this project, we aim to extend the benefits of our previous efforts by developing and implementing an interactive, evidence-based clinical decision support tool to optimize care for children and adolescents presenting to a general or non-pediatric ED with acute abdominal pain. The results of this project will extend our understanding of how to maximize the clinical return on massive public and private sector investments being made in sophisticated EHR systems. If successful, this flexible decision support tool could be adapted and implemented broadly in a range of acute care settings to both standardize and personalize care delivered to pediatric patients.